I think that the 2d universe concept is probably a useful tool for people who want to deal with the physics of information management. I don’t try to visualize it too much, because my puny human brain isn’t designed to do that. But I can respect the predictive power of these kinds of tools that physicists use.

This is where theoretical physics starts to lose me (my support, not my knowledge, which is not much to start with). I remember way back when I took Quantum Mech 101 in college, thinking to myself, something’s not quite kosher here. They seem to regard certain of the equations as actually existing as real things that interact with the physical universe versus just useful, though highly complex, tools. This 2D stuff sounds like that.

I also start to wonder, at those extreme small scales, how do they know they’re looking at something real versus a “ghost” of the tools they’re using?

Flatland, published in 1882. Author: Edwin Abbott. I guess he was ahead of his time. And who knew that squares, polygons, etc., face some of the same social problems as we, in our less dimensionally-challenged existence?

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As a fabrication of our own consciousness, our assignations of meaning are no less “real”, but since humans and the fabrications of our consciousness are routinely fraught with error, it makes sense, to me, to, sometimes, question such fabrications.

It boils down to the fact that the informational content of a blackhole is proportional to the size of the surface of the event horizon of a black hole, instead to its volume. Now the event horizon is the border from behind which no information can reach us because it would need to be faster than light. We have something similar with the universe as a whole: because two points in the universe move from each other the faster they are from each other, there is an event horizon in the sense that they move from each other faster than light, so no information can be exchanged anymore. So the whole of the 3-dimensional visible universe has the same information content as the two dimensional surface of the event horizon.